PRACTICAL CASES OF THE USE OF MOLECULAR TECHNIQUES TO CHARACTERIZE MICROBIAL DETERIORATION OF METALLIC STRUCTURES IN INDUSTRY

摘要

Two specific cases of applying molecular techniques for deciphering the role of microorganisms in industrial processes are presented: an offshore seawater injection system and a wastewater treatment plant. In the first case, deoxyribonucleic acid (DNA) was extracted from a water sample taken from an offshore seawater injection system and from enrichment cultures from the same sample. The V3 hypervariable region of the 16S rDNA gene was amplified by the polymerase chain reaction (PCR) and bacterial diversity was studied using denaturing gel gradient electrophoresis (DGGE). DGGE monitoring of the system showed that persistent bacteria were present, mainly facultative anaerobic bacteria as Shewanella and Vibrio. These bacteria are also suspected to resist the biocide treatment used in this system. A second case was based on a study of wastewater treatment plants where massive sulfide production generally occurs during organic matter mineralization. Different observations suggested that the addition of nitrate to the input waters reduced the production of sulfides and so significantly decreased potential biocorrosion effects on metallic structures at the plant. Ribonucleic acid (RNA) was extracted, and the complex microbial communities present in the wastewaters were analyzed by constructing 16S rRNA gene libraries and by quantitative real time RT-PCR (reverse transcription-polymerase chain reaction) amplification methods using group and species-specific primers. Results suggested that sulfate-reducing bacteria (major sulfide producers) were not inhibited by nitrate treatment and their interaction with sulfur- oxidizing bacteria (sulfide consumers) results in a low net production of sulfides leading to decreasing biocorrosion effects.